This invention is related to electrical connectors and, in particular, to connectors of the type used to connect mobile devices together for data transfer.
This application deals with electrical connectors, the type of which could be used to connect mobile communications or mobile data processing devices together. As an example, the connector could be used to connect various accessories, such as a GPS device, to a cellular telephone. Several difficulties exist with current state of the art connectors and other connectors existing in the prior art.
One problem is that of contact resistance at the point where the leads of the connector contact the contacts on the printed circuit board. Because of asperities existing at a microstructure level on the material of which the leads of the connector and the contact on the circuit board are constructed, the amount of surface area that contacts the connection point for the connector is dependent upon the pressure used to hold the contact against the connection point. The contact resistance is a function of the amount of surface area of the contact which contacts the connection point, and occurs at every contact interface surface. Connectors of the prior art are constructed using two piston like contacts separated by a spring which is compressed and which pushes the piston shaped contacts against their mating contact points. The two interfaces where the spring meets the piston shaped contacts introduces additional contact interface surfaces at which contact resistance exists, thereby limiting the current carrying capacity of the connection. In some cases this may render the connection unusable for the type of accessories that one may wish to connect to the cellular phone. It is therefore desirable to eliminate the contact interfaces between the spring and the piston shaped contact surfaces to lower the contact resistance introduced thereby.
It is possible to eliminate the additional contact interface surfaces with a type of cantilever spring design. In this type of design, each contact contains an xe2x80x9cSxe2x80x9d or xe2x80x9cZxe2x80x9d-shaped bend in the connection between the two contacts at opposite ends of the connector. This cantilever spring type of arrangement will force the contacts outwardly when they are compressed. However, the problem with this type of design is that the size of the hole into which the contact can be housed is limited. It is desirable to have the contacts disposed in holes of very small diameter. Often, the desired diameter holes are so small that the cantilevered type design is untenable. It is therefore necessary and desirable to use the coil type spring, while still eliminating the additional contact interface surfaces between the spring and the contacts.
Another problem with the prior art design is that the geometry of the contacts at the point of contact is not optimal and it is therefore desirable to replace the straight type of contacts with a shape that is better suited for making the contact with the contact point.
The connector of the current invention utilizes a unique one-piece design for each contact in the connector and consists of a coiled spring having loops at each end which are used as the actual contacts. The one-piece construction eliminates the additional contact interface surfaces between the coiled spring and the contacts and the looped ends provide more stability and a good geometry to connect with the contact point. This type of connector provides the advantage of eliminating the additional contact interface surfaces while at the same time being able to fit into a extremely small diameter hole. Another advantage of this design is the savings involved in the assembly of the connector. Because both contacts and the spring are of unitary construction, it is much less labor intensive to assemble this type of connector then it is to assemble the piston and spring type connector.